If the key to price in real estate is “location, location, location,” the key to success in verit-style documentaries is “access, access, access” — which is what “Cartel Land” offers and what makes it compelling.

The drug war in Mexico has generated numerous documentaries, including the recent “Narco Cultura” and “Western.” “Cartel Land,” a double prize winner at Sundance, is one of the most involving because of where it goes and what it shows us.

Filmmaker Matthew Heineman — who directed, co-edited and was the main cinematographer — says in a statement that “it took many months to gain the trust and to gain the access that I needed to tell this story.”

What he”s referring to are “Cartel Land”s” twin protagonists — vigilantes from two countries and cultures who are determined to fight back against the violence brought by the Mexican drug cartels to everything they touch.

Jos Mireles lives and works in the Mexican state of Michoacn, where taking on the cartels seemed to him and those around him to be the only way to stay alive.

Tim “Nailer” Foley is an American living in Arizona”s Altar Valley, whose fear of the cartels” extending their influence deeper into the United States is fueled by elements of suspicion of the federal government and opposition to illegal immigration, which he believes the cartels have a hand in.

After Heineman, whose first film was “Escape Fire: The Fight to Rescue American Healthcare,” spent months winning trust, he spent a similar amount of time filming and observing. The result is a film with the kind of unpredictable events only reality provides.

Before getting to its main characters, “Cartel Land” opens with one of its most chilling scenes — a middle-of-the-night visit to an outdoor meth lab a la “Breaking Bad.” The man in charge, masked, as are all his confederates, quietly mixes the chemicals and boasts, “We are No. 1 here in Michoacn, the most quantity and the best quality.”

He also sounds bleakly apologetic about his line of work. “What are you going to do? — we come from poverty,” he says. “If we start paying attention to our hearts, we get screwed over. We will do this as long as God allows.”

This sense that the world does not appreciate the reasons he and others are in this line of work is one of “Cartel Land”s” themes. Both Foley and Mireles sound similar notes. And Heineman is always dispassionate, leaving us to make whatever comparisons we feel are appropriate.

Foley, who knows that “vigilantes have been given a bad name,” sees his team as no more than “concerned citizens arming themselves.” He and his men play soldier at the border areas, stopping small groups of undocumented aliens and hoping for bigger fish.

In Michoacn, where the Knights Templar cartel (an offshoot of the dreaded Zetas) is a very visible presence, the situation on the ground is more compelling and more dangerous.

Mireles, a doctor by profession, is the charismatic founder and leader of Grupo de Autodefensa, a band of armed citizens who go from town to town asking residents to help them circulate house to house to evict cartel personnel.

“Cartel Land”s” most astonishing footage comes in the town of Apo. After the Mexican army, no fan of vigilante action, swoops in to disarm the Autodefensas, the townspeople rise up against the soldiers and drive them out of town. But while this might sound like a classic Robin Hood story, reality has more twists in store, and figuring out exactly who the good guys are becomes increasingly problematic.

While acting as his own cinematographer, Heineman exposed himself to dangerous, gunfire-filled situations but managed to create memorable images along the way.

If the key to price in real estate is “location, location, location,” the key to success in verit-style documentaries is “access, access, access” — which is what “Cartel Land” offers and what makes it compelling.

The drug war in Mexico has generated numerous documentaries, including the recent “Narco Cultura” and “Western.” “Cartel Land,” a double prize winner at Sundance, is one of the most involving because of where it goes and what it shows us.

Filmmaker Matthew Heineman — who directed, co-edited and was the main cinematographer — says in a statement that “it took many months to gain the trust and to gain the access that I needed to tell this story.”

What he”s referring to are “Cartel Land”s” twin protagonists — vigilantes from two countries and cultures who are determined to fight back against the violence brought by the Mexican drug cartels to everything they touch.

Jos Mireles lives and works in the Mexican state of Michoacn, where taking on the cartels seemed to him and those around him to be the only way to stay alive.

Tim “Nailer” Foley is an American living in Arizona”s Altar Valley, whose fear of the cartels” extending their influence deeper into the United States is fueled by elements of suspicion of the federal government and opposition to illegal immigration, which he believes the cartels have a hand in.

After Heineman, whose first film was “Escape Fire: The Fight to Rescue American Healthcare,” spent months winning trust, he spent a similar amount of time filming and observing. The result is a film with the kind of unpredictable events only reality provides.

Before getting to its main characters, “Cartel Land” opens with one of its most chilling scenes — a middle-of-the-night visit to an outdoor meth lab a la “Breaking Bad.” The man in charge, masked, as are all his confederates, quietly mixes the chemicals and boasts, “We are No. 1 here in Michoacn, the most quantity and the best quality.”

He also sounds bleakly apologetic about his line of work. “What are you going to do? — we come from poverty,” he says. “If we start paying attention to our hearts, we get screwed over. We will do this as long as God allows.”

This sense that the world does not appreciate the reasons he and others are in this line of work is one of “Cartel Land”s” themes. Both Foley and Mireles sound similar notes. And Heineman is always dispassionate, leaving us to make whatever comparisons we feel are appropriate.

Foley, who knows that “vigilantes have been given a bad name,” sees his team as no more than “concerned citizens arming themselves.” He and his men play soldier at the border areas, stopping small groups of undocumented aliens and hoping for bigger fish.

In Michoacn, where the Knights Templar cartel (an offshoot of the dreaded Zetas) is a very visible presence, the situation on the ground is more compelling and more dangerous.

Mireles, a doctor by profession, is the charismatic founder and leader of Grupo de Autodefensa, a band of armed citizens who go from town to town asking residents to help them circulate house to house to evict cartel personnel.

“Cartel Land”s” most astonishing footage comes in the town of Apo. After the Mexican army, no fan of vigilante action, swoops in to disarm the Autodefensas, the townspeople rise up against the soldiers and drive them out of town. But while this might sound like a classic Robin Hood story, reality has more twists in store, and figuring out exactly who the good guys are becomes increasingly problematic.

While acting as his own cinematographer, Heineman exposed himself to dangerous, gunfire-filled situations but managed to create memorable images along the way.